Cleaning compositions for cleaning fabrics such as clothing, for hand-cleaning dishes, or for washing body parts, commonly contain sudsing ingredients such as surfactants or free fatty acids. Especially during washing of clothes and fabrics, dishes, and body parts, where the user is very involved with the washing process, a large volume of suds is initially desirable, because it indicates to the user that sufficient surfactant is present and is performing the desired cleaning.
Though a large volume of suds may be desirable during cleaning, it paradoxically typically takes from 3 to 6 rinses to remove suds to the satisfaction of the person washing. This can add up to a great amount of water being used every day for rinsing around the world—typically about 5 to 10 tons of water per year per household in countries such as India and China, where hand-washing of laundry is standard practice. Because water is often a limited resource, especially in hand washing countries, the use of water for rinsing reduces the amount available for other possible uses such as irrigation, drinking and bathing. Depending on the location and the local practice, there may also be an added energy or labor cost involved with rinsing so many times and with so much water.
Suds suppressors are well-known in, for example, automatic dishwashing detergents and laundry detergents for front-loading washing machines. But when consumers who are accustomed to seeing suds during the wash, an absence of suds leads the consumer to believe that the cleaning composition is not performing to expectations. Because typical suds suppressors do not distinguish between the wash and rinse conditions, they do not solve the problem of providing suds during use while still reducing the need for rinsing.
During rinsing, the typical user of laundry detergents, hand dishwashing detergents, and personal bar soaps typically believes that if suds are still present, then what is being washed is not yet “clean” until the suds are not seen in the rinse. However, it has been found that fewer rinses can sufficiently remove sudsing ingredients such as surfactants. As such, if consumer perception can be overcome in this regard, use of water for rinsing can be reduced with little or no adverse effects to the typical user of the cleaning composition.
Accordingly, because in many countries water and other resources are becoming ever more scarce, the need exists for an effective way to reduce the amount of water used for rinsing of laundry, dishes, and body parts without sacrificing cleaning efficiency and effectiveness. The inventors have discovered that some or all of the above mentioned needs can be at least partially fulfilled through cleaning compositions according to embodiments described below, in which a pH-switchable co-surfactant is present.